The application is directed to an all-solid-state battery. In particular, the application relates to an all-solid-state metal-metal battery comprising ion conducting ceramic solids as the electrolytes.
Rechargeable batteries become increasingly important in daily life. It is particularly desirable to have a rechargeable battery with both high energy density and high power density.
Lithium (Li)-ion battery is superior to nickel-metal hydride (Ni-MH) battery because Li-ion battery has higher energy density and power density. Conventional Li-ion batteries are based on the “rocking-chair” principle of simultaneous Li ion extraction and insertion in both anode and cathode. Li ions are transferred through electrolytes between the two electrodes during the charging/discharging processes, in concert with electron transport through the external circuit. Inside a Li-ion battery, therefore, Li ions are a single type of carriers to be released and to receive electrons. The power density of a Li-ion battery is related to the diffusion rate of Li ions in the electrolytes. The energy density, however, is related to the host-guest relationship. Therefore, the energy density of a Li-ion battery is controlled by the electrode host structure.
Since the commercialization of Li-ion batteries in the early 1990s, tremendous efforts have been devoted to improving the performance of Li-ion batteries. However, even the most advanced Li-ion battery is not considered to be viable as a power source capable to meet the demands for a commercial electric vehicle (EV) in the future. For example, for a 300 mile range EV to have a power train equivalent to current conventional internal combustion engine vehicles, an EV battery pack having an energy density of approximately 2000 Wh/L is required. This energy density is close to the theoretical limit of a lithium ion active material.
In addition, batteries typically do not have both high energy density and high power density because usually there is a trade-off relationship between these two features. An ultimate rechargeable battery with both high enough energy density and high enough power density for automotive applications is yet to be developed. Much effort has been devoted to the development of such post Li-ion batteries.
One idea to obtain a battery with both high energy density and high power density is to go beyond the conventional “rocking-chair” principle.
For example, Li-air batteries use inexhaustible oxygen from outside (i.e. air) instead of storing an oxidizer inside. Therefore, a Li-air battery has much higher energy density when compared with a conventional Li-ion battery and have potential application in the field of long-range electric vehicles. However, unsolved fundamental problems such as poor oxygen redox kinetics at the positive electrode and deleterious volume and morphology changes at the negative electrode greatly limit the practical application of Li-air batteries. Therefore, Li-air batteries still remain as a research topic today.
Placke et al. described in J. Electrochem. Soc., 159(11), pp. A1755-A1765 (2012) a “dual ion” cell, in which dual mobile ions from the electrolyte act as carriers inside the battery. That is, both cations and anions from the electrolyte take part in the charge/discharge reactions in the dual ion cell. Although the dual-ion systems described by Placke et al. have excellent charge/discharge cycling behavior, the maximum theoretical energy densities does not appear to be sufficient for automotive applications.
Takada et al. described in Solid State Ionics, 158, pp. 269-274 (2003) a solid-state Li battery using graphite as the anode, LiCoO2 as the cathode, LiI—Li2S—P2S5 glass as the anolyte, and Li3PO4—Li2S—SiS2 glass or Li2S—GeS2—P2S5 crystalline material as the catholyte. It should be noted that although two kinds of Li-ion conducting solid electrolytes are used in the battery, Li-ions are still the single type of carriers transported in both electrolytes. The energy density of such solid-state Li batteries is found comparable with the energy density of commercial Li-ion batteries.
Wang et al. described in Electrochem. Commun., 11, pp. 1834-1837 (2009) a metal-metal battery, in which a Li-anode in a non-aqueous anolyte and a Cu-cathode in an aqueous catholyte are separated by LISICON, a Li super-ionic conductor glass film. In this metal-metal battery, the cathode reaction of Li insertion/extraction in conventional Li-ion batteries is replaced by Cu dissolution/deposition. Therefore, the Cu-cathode is renewable. It is noted that two different cations—Li cations and Cu cations—exist in this metal-metal battery. However, because the anolyte and the catholyte is separated by a glass film only permeable to Li ions, Cu ions only exist in the catholyte while Li ions exist in both the anolyte and the catholyte.
It is known that Li ions are mobile carrier solvated in a solution, whereas they diffuse alone in a conducting solid. Because the metal-metal battery described in Wang et al. contains both solutions and conducting solids, Li ions are transported from one electrode to the other through complicated steps, that is, desolvation on one electrode, solvation in one electrolyte, desolvaton on the LISICON film, solvation in the other electrolyte, and desolvation on the other electrode. This would cause interfacial resistance changes with changing state of charge/discharge so that the overall battery resistance and performance would be adversely affected.
An all-solid-state battery has potential in mitigating or hindering such a complicated solvation-desolvation process. In addition, metals generally have higher theoretical capacity than traditional intercalation materials and the metal dissolution/deposition mechanism is more promising than the conventional “rocking chair” principle to achieve higher energy density of the battery. Recognizing all these potentials of all-solid-state metal-metal batteries, inventors of the present invention are directing effort and resources to the study of such batteries in order to obtain a next generation solid-state metal-metal battery with both high energy density and high power density.
Accordingly, an object of the present invention is to provide an all-solid-state metal-metal battery of higher energy density and higher power density than the conventional Li-ion batteries. Another object is to provide an all-solid-state metal-metal battery with simple structures. These and other objects, features, and advantages of the present invention will become more evident from the following discussion as well as the drawings.